diff --git a/dist/sqlite3.c b/dist/sqlite3.c
index 6e9d2b3..51690ad 100644
--- a/dist/sqlite3.c
+++ b/dist/sqlite3.c
@@ -656,7 +656,7 @@
 */
 #define SQLITE_VERSION        "3.7.4"
 #define SQLITE_VERSION_NUMBER 3007004
-#define SQLITE_SOURCE_ID      "2010-12-07 20:14:09 a586a4deeb25330037a49df295b36aaf624d0f45"
+#define SQLITE_SOURCE_ID      "2011-02-20 03:40:59 e2616004dfaf61d776e448693971b6478552a635"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
@@ -19167,27 +19167,21 @@
 ** current locale settings.  This is important for SQLite because we
 ** are not able to use a "," as the decimal point in place of "." as
 ** specified by some locales.
-**
-** Oops:  The first two arguments of sqlite3_snprintf() are backwards
-** from the snprintf() standard.  Unfortunately, it is too late to change
-** this without breaking compatibility, so we just have to live with the
-** mistake.
-**
-** sqlite3_vsnprintf() is the varargs version.*/
-SQLITE_API char *sqlite3_vsnprintf(int n, char *zBuf, const char *zFormat, va_list ap){
-  StrAccum acc;
-  if( n<=0 ) return zBuf;
-  sqlite3StrAccumInit(&acc, zBuf, n, 0);
-  acc.useMalloc = 0;
-  sqlite3VXPrintf(&acc, 0, zFormat, ap);
-  return sqlite3StrAccumFinish(&acc);
-}
+*/
 SQLITE_API char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
   char *z;
   va_list ap;
+  StrAccum acc;
+
+  if( n<=0 ){
+    return zBuf;
+  }
+  sqlite3StrAccumInit(&acc, zBuf, n, 0);
+  acc.useMalloc = 0;
   va_start(ap,zFormat);
-  z = sqlite3_vsnprintf(n, zBuf, zFormat, ap);
+  sqlite3VXPrintf(&acc, 0, zFormat, ap);
   va_end(ap);
+  z = sqlite3StrAccumFinish(&acc);
   return z;
 }
 
@@ -37630,11 +37624,37 @@
   return rc;
 }
 
+
+/*
+** Update the value of the change-counter at offsets 24 and 92 in
+** the header and the sqlite version number at offset 96.
+**
+** This is an unconditional update.  See also the pager_incr_changecounter()
+** routine which only updates the change-counter if the update is actually
+** needed, as determined by the pPager->changeCountDone state variable.
+*/
+static void pager_write_changecounter(PgHdr *pPg){
+  u32 change_counter;
+
+  /* Increment the value just read and write it back to byte 24. */
+  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
+  put32bits(((char*)pPg->pData)+24, change_counter);
+
+  /* Also store the SQLite version number in bytes 96..99 and in
+  ** bytes 92..95 store the change counter for which the version number
+  ** is valid. */
+  put32bits(((char*)pPg->pData)+92, change_counter);
+  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
+}
+
 /*
 ** This function is a wrapper around sqlite3WalFrames(). As well as logging
 ** the contents of the list of pages headed by pList (connected by pDirty),
 ** this function notifies any active backup processes that the pages have
-** changed. 
+** changed.
+**
+** The list of pages passed into this routine is always sorted by page number.
+** Hence, if page 1 appears anywhere on the list, it will be the first page.
 */ 
 static int pagerWalFrames(
   Pager *pPager,                  /* Pager object */
@@ -37644,8 +37664,19 @@
   int syncFlags                   /* Flags to pass to OsSync() (or 0) */
 ){
   int rc;                         /* Return code */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_CHECK_PAGES)
+  PgHdr *p;                       /* For looping over pages */
+#endif
 
   assert( pPager->pWal );
+#ifdef SQLITE_DEBUG
+  /* Verify that the page list is in accending order */
+  for(p=pList; p && p->pDirty; p=p->pDirty){
+    assert( p->pgno < p->pDirty->pgno );
+  }
+#endif
+
+  if( pList->pgno==1 ) pager_write_changecounter(pList);
   rc = sqlite3WalFrames(pPager->pWal, 
       pPager->pageSize, pList, nTruncate, isCommit, syncFlags
   );
@@ -37657,9 +37688,8 @@
   }
 
 #ifdef SQLITE_CHECK_PAGES
-  {
-    PgHdr *p;
-    for(p=pList; p; p=p->pDirty) pager_set_pagehash(p);
+  for(p=pList; p; p=p->pDirty){
+    pager_set_pagehash(p);
   }
 #endif
 
@@ -38684,6 +38714,7 @@
       char *pData;                                   /* Data to write */    
 
       assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
+      if( pList->pgno==1 ) pager_write_changecounter(pList);
 
       /* Encode the database */
       CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData);
@@ -40204,7 +40235,13 @@
 /*
 ** This routine is called to increment the value of the database file 
 ** change-counter, stored as a 4-byte big-endian integer starting at 
-** byte offset 24 of the pager file.
+** byte offset 24 of the pager file.  The secondary change counter at
+** 92 is also updated, as is the SQLite version number at offset 96.
+**
+** But this only happens if the pPager->changeCountDone flag is false.
+** To avoid excess churning of page 1, the update only happens once.
+** See also the pager_write_changecounter() routine that does an 
+** unconditional update of the change counters.
 **
 ** If the isDirectMode flag is zero, then this is done by calling 
 ** sqlite3PagerWrite() on page 1, then modifying the contents of the
@@ -40245,7 +40282,6 @@
 
   if( !pPager->changeCountDone && pPager->dbSize>0 ){
     PgHdr *pPgHdr;                /* Reference to page 1 */
-    u32 change_counter;           /* Initial value of change-counter field */
 
     assert( !pPager->tempFile && isOpen(pPager->fd) );
 
@@ -40258,21 +40294,13 @@
     ** direct mode, page 1 is always held in cache and hence the PagerGet()
     ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
     */
-    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
+    if( !DIRECT_MODE && rc==SQLITE_OK ){
       rc = sqlite3PagerWrite(pPgHdr);
     }
 
     if( rc==SQLITE_OK ){
-      /* Increment the value just read and write it back to byte 24. */
-      change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
-      change_counter++;
-      put32bits(((char*)pPgHdr->pData)+24, change_counter);
-
-      /* Also store the SQLite version number in bytes 96..99 and in
-      ** bytes 92..95 store the change counter for which the version number
-      ** is valid. */
-      put32bits(((char*)pPgHdr->pData)+92, change_counter);
-      put32bits(((char*)pPgHdr->pData)+96, SQLITE_VERSION_NUMBER);
+      /* Actually do the update of the change counter */
+      pager_write_changecounter(pPgHdr);
 
       /* If running in direct mode, write the contents of page 1 to the file. */
       if( DIRECT_MODE ){
@@ -41707,21 +41735,6 @@
 #endif
 
 /*
-** WAL tracing logic added to search for an SQLITE_PROTOCOL error.
-*/
-static void walTrace(const char *zFormat, ...){
-  va_list ap;
-  char zMsg[100];
-  va_start(ap, zFormat);
-  sqlite3_vsnprintf(sizeof(zMsg), zMsg, zFormat, ap);
-  va_end(ap);
-#ifdef SQLITE_WAL_TRACE
-  fprintf(stdout, "WALTRACE: [%s]\n", zMsg); fflush(stdout);
-#endif
-  sqlite3_log(99, "%s", zMsg);
-}
-
-/*
 ** The maximum (and only) versions of the wal and wal-index formats
 ** that may be interpreted by this version of SQLite.
 **
@@ -41979,7 +41992,6 @@
     apNew = (volatile u32 **)sqlite3_realloc((void *)pWal->apWiData, nByte);
     if( !apNew ){
       *ppPage = 0;
-      walTrace("realloc(%d) in walIndexPage()", nByte);
       return SQLITE_NOMEM;
     }
     memset((void*)&apNew[pWal->nWiData], 0,
@@ -41998,7 +42010,6 @@
           pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
       );
     }
-    if( rc ) walTrace("xShmMap():%d in walIndexPage(iPage=%d)",rc,iPage);
   }
 
   *ppPage = pWal->apWiData[iPage];
@@ -43043,7 +43054,8 @@
   szPage = (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
   testcase( szPage<=32768 );
   testcase( szPage>=65536 );
-  if( pWal->hdr.mxFrame==0 ) return SQLITE_OK;
+  pInfo = walCkptInfo(pWal);
+  if( pInfo->nBackfill>=pWal->hdr.mxFrame ) return SQLITE_OK;
 
   /* Allocate the iterator */
   rc = walIteratorInit(pWal, &pIter);
@@ -43065,7 +43077,6 @@
   */
   mxSafeFrame = pWal->hdr.mxFrame;
   mxPage = pWal->hdr.nPage;
-  pInfo = walCkptInfo(pWal);
   for(i=1; i<WAL_NREADER; i++){
     u32 y = pInfo->aReadMark[i];
     if( mxSafeFrame>=y ){
@@ -43295,7 +43306,6 @@
   assert( badHdr==0 || pWal->writeLock==0 );
   if( badHdr && SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
     pWal->writeLock = 1;
-    walTrace("trying walIndexTryHdr w/lock");
     if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
       badHdr = walIndexTryHdr(pWal, pChanged);
       if( badHdr ){
@@ -43303,16 +43313,13 @@
         ** a WRITE lock, it can only mean that the header is corrupted and
         ** needs to be reconstructed.  So run recovery to do exactly that.
         */
-        walTrace("walIndexTryHdr() failed w/lock");
         rc = walIndexRecover(pWal);
-        if( rc ) walTrace("walIndexRecover():%d", rc);
         *pChanged = 1;
       }
     }
     pWal->writeLock = 0;
     walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
   }
-  else if(badHdr) walTrace("walLockExcl():%d in walIndexReadHdr()", rc);
 
   /* If the header is read successfully, check the version number to make
   ** sure the wal-index was not constructed with some future format that
@@ -43390,11 +43397,31 @@
 
   assert( pWal->readLock<0 );     /* Not currently locked */
 
-  /* Take steps to avoid spinning forever if there is a protocol error. */
+  /* Take steps to avoid spinning forever if there is a protocol error.
+  **
+  ** Circumstances that cause a RETRY should only last for the briefest
+  ** instances of time.  No I/O or other system calls are done while the
+  ** locks are held, so the locks should not be held for very long. But 
+  ** if we are unlucky, another process that is holding a lock might get
+  ** paged out or take a page-fault that is time-consuming to resolve, 
+  ** during the few nanoseconds that it is holding the lock.  In that case,
+  ** it might take longer than normal for the lock to free.
+  **
+  ** After 5 RETRYs, we begin calling sqlite3OsSleep().  The first few
+  ** calls to sqlite3OsSleep() have a delay of 1 microsecond.  Really this
+  ** is more of a scheduler yield than an actual delay.  But on the 10th
+  ** an subsequent retries, the delays start becoming longer and longer, 
+  ** so that on the 100th (and last) RETRY we delay for 21 milliseconds.
+  ** The total delay time before giving up is less than 1 second.
+  */
   if( cnt>5 ){
-    walTrace("cnt=%d",cnt);
-    if( cnt>100 ) return SQLITE_PROTOCOL;
-    sqlite3OsSleep(pWal->pVfs, 1);
+    int nDelay = 1;                      /* Pause time in microseconds */
+    if( cnt>100 ){
+      VVA_ONLY( pWal->lockError = 1; )
+      return SQLITE_PROTOCOL;
+    }
+    if( cnt>=10 ) nDelay = (cnt-9)*238;  /* Max delay 21ms. Total delay 996ms */
+    sqlite3OsSleep(pWal->pVfs, nDelay);
   }
 
   if( !useWal ){
@@ -43451,18 +43478,12 @@
         ** have started to backfill the appended frames but crashed before
         ** it finished. Leaving a corrupt image in the database file.
         */
-        if( cnt>5 ){
-          walTrace("wal read/write race - writer won");
-        }
         walUnlockShared(pWal, WAL_READ_LOCK(0));
         return WAL_RETRY;
       }
       pWal->readLock = 0;
       return SQLITE_OK;
     }else if( rc!=SQLITE_BUSY ){
-      if( cnt>5 ){
-        walTrace("walLockShared(0):%d in walTryBeginRead", rc);
-      }
       return rc;
     }
   }
@@ -43482,28 +43503,9 @@
       mxI = i;
     }
   }
-  if( mxI==0 ){
-    /* If we get here, it means that all of the aReadMark[] entries between
-    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
-    ** be mxFrame, then retry.
-    */
-    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
-    if( rc==SQLITE_OK ){
-      pInfo->aReadMark[1] = pWal->hdr.mxFrame;
-      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);
-      rc = WAL_RETRY;
-      if( cnt>5 ){
-        walTrace("aReadMark[1] <- %d", pWal->hdr.mxFrame);
-      }
-    }else if( rc==SQLITE_BUSY ){
-      rc = WAL_RETRY;
-      if( cnt>5 ){
-        walTrace("aReadMark[1] is busy");
-      }
-    }
-    return rc;
-  }else{
-    if( mxReadMark < pWal->hdr.mxFrame ){
+  /* There was once an "if" here. The extra "{" is to preserve indentation. */
+  {
+    if( mxReadMark < pWal->hdr.mxFrame || mxI==0 ){
       for(i=1; i<WAL_NREADER; i++){
         rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
         if( rc==SQLITE_OK ){
@@ -43512,19 +43514,17 @@
           walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
           break;
         }else if( rc!=SQLITE_BUSY ){
-          if( cnt>5 ){
-            walTrace("walLockExclusive(%d):%d", i, rc);
-          }
           return rc;
         }
       }
     }
+    if( mxI==0 ){
+      assert( rc==SQLITE_BUSY );
+      return WAL_RETRY;
+    }
 
     rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
     if( rc ){
-      if( cnt>5 ){
-        walTrace("walLockShared(mxI=%d):%d", mxI, rc);
-      }
       return rc==SQLITE_BUSY ? WAL_RETRY : rc;
     }
     /* Now that the read-lock has been obtained, check that neither the
@@ -43582,6 +43582,10 @@
   do{
     rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
   }while( rc==WAL_RETRY );
+  testcase( (rc&0xff)==SQLITE_BUSY );
+  testcase( (rc&0xff)==SQLITE_IOERR );
+  testcase( rc==SQLITE_PROTOCOL );
+  testcase( rc==SQLITE_OK );
   return rc;
 }
 
@@ -43899,6 +43903,8 @@
     volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
     assert( pInfo->nBackfill==pWal->hdr.mxFrame );
     if( pInfo->nBackfill>0 ){
+      u32 salt1;
+      sqlite3_randomness(4, &salt1);
       rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
       if( rc==SQLITE_OK ){
         /* If all readers are using WAL_READ_LOCK(0) (in other words if no
@@ -43916,7 +43922,7 @@
         pWal->nCkpt++;
         pWal->hdr.mxFrame = 0;
         sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
-        sqlite3_randomness(4, &aSalt[1]);
+        aSalt[1] = salt1;
         walIndexWriteHdr(pWal);
         pInfo->nBackfill = 0;
         for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
@@ -43933,6 +43939,10 @@
       int notUsed;
       rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
     }while( rc==WAL_RETRY );
+    assert( (rc&0xff)!=SQLITE_BUSY ); /* BUSY not possible when useWal==1 */
+    testcase( (rc&0xff)==SQLITE_IOERR );
+    testcase( rc==SQLITE_PROTOCOL );
+    testcase( rc==SQLITE_OK );
   }
   return rc;
 }
@@ -47638,7 +47648,7 @@
                                    pageSize-usableSize);
       return rc;
     }
-    if( nPageHeader>nPageFile ){
+    if( (pBt->db->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
       rc = SQLITE_CORRUPT_BKPT;
       goto page1_init_failed;
     }
diff --git a/dist/sqlite3.c.orig b/dist/sqlite3.c.orig
index a5b93c4..6716fc3 100644
--- a/dist/sqlite3.c.orig
+++ b/dist/sqlite3.c.orig
@@ -652,7 +652,7 @@
 */
 #define SQLITE_VERSION        "3.7.4"
 #define SQLITE_VERSION_NUMBER 3007004
-#define SQLITE_SOURCE_ID      "2010-12-07 20:14:09 a586a4deeb25330037a49df295b36aaf624d0f45"
+#define SQLITE_SOURCE_ID      "2011-02-20 03:40:59 e2616004dfaf61d776e448693971b6478552a635"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
@@ -37617,11 +37617,37 @@
   return rc;
 }
 
+
+/*
+** Update the value of the change-counter at offsets 24 and 92 in
+** the header and the sqlite version number at offset 96.
+**
+** This is an unconditional update.  See also the pager_incr_changecounter()
+** routine which only updates the change-counter if the update is actually
+** needed, as determined by the pPager->changeCountDone state variable.
+*/
+static void pager_write_changecounter(PgHdr *pPg){
+  u32 change_counter;
+
+  /* Increment the value just read and write it back to byte 24. */
+  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
+  put32bits(((char*)pPg->pData)+24, change_counter);
+
+  /* Also store the SQLite version number in bytes 96..99 and in
+  ** bytes 92..95 store the change counter for which the version number
+  ** is valid. */
+  put32bits(((char*)pPg->pData)+92, change_counter);
+  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
+}
+
 /*
 ** This function is a wrapper around sqlite3WalFrames(). As well as logging
 ** the contents of the list of pages headed by pList (connected by pDirty),
 ** this function notifies any active backup processes that the pages have
-** changed. 
+** changed.
+**
+** The list of pages passed into this routine is always sorted by page number.
+** Hence, if page 1 appears anywhere on the list, it will be the first page.
 */ 
 static int pagerWalFrames(
   Pager *pPager,                  /* Pager object */
@@ -37631,8 +37657,19 @@
   int syncFlags                   /* Flags to pass to OsSync() (or 0) */
 ){
   int rc;                         /* Return code */
+#if defined(SQLITE_DEBUG) || defined(SQLITE_CHECK_PAGES)
+  PgHdr *p;                       /* For looping over pages */
+#endif
 
   assert( pPager->pWal );
+#ifdef SQLITE_DEBUG
+  /* Verify that the page list is in accending order */
+  for(p=pList; p && p->pDirty; p=p->pDirty){
+    assert( p->pgno < p->pDirty->pgno );
+  }
+#endif
+
+  if( pList->pgno==1 ) pager_write_changecounter(pList);
   rc = sqlite3WalFrames(pPager->pWal, 
       pPager->pageSize, pList, nTruncate, isCommit, syncFlags
   );
@@ -37644,9 +37681,8 @@
   }
 
 #ifdef SQLITE_CHECK_PAGES
-  {
-    PgHdr *p;
-    for(p=pList; p; p=p->pDirty) pager_set_pagehash(p);
+  for(p=pList; p; p=p->pDirty){
+    pager_set_pagehash(p);
   }
 #endif
 
@@ -38671,6 +38707,7 @@
       char *pData;                                   /* Data to write */    
 
       assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
+      if( pList->pgno==1 ) pager_write_changecounter(pList);
 
       /* Encode the database */
       CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData);
@@ -40191,7 +40228,13 @@
 /*
 ** This routine is called to increment the value of the database file 
 ** change-counter, stored as a 4-byte big-endian integer starting at 
-** byte offset 24 of the pager file.
+** byte offset 24 of the pager file.  The secondary change counter at
+** 92 is also updated, as is the SQLite version number at offset 96.
+**
+** But this only happens if the pPager->changeCountDone flag is false.
+** To avoid excess churning of page 1, the update only happens once.
+** See also the pager_write_changecounter() routine that does an 
+** unconditional update of the change counters.
 **
 ** If the isDirectMode flag is zero, then this is done by calling 
 ** sqlite3PagerWrite() on page 1, then modifying the contents of the
@@ -40232,7 +40275,6 @@
 
   if( !pPager->changeCountDone && pPager->dbSize>0 ){
     PgHdr *pPgHdr;                /* Reference to page 1 */
-    u32 change_counter;           /* Initial value of change-counter field */
 
     assert( !pPager->tempFile && isOpen(pPager->fd) );
 
@@ -40245,21 +40287,13 @@
     ** direct mode, page 1 is always held in cache and hence the PagerGet()
     ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
     */
-    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
+    if( !DIRECT_MODE && rc==SQLITE_OK ){
       rc = sqlite3PagerWrite(pPgHdr);
     }
 
     if( rc==SQLITE_OK ){
-      /* Increment the value just read and write it back to byte 24. */
-      change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers);
-      change_counter++;
-      put32bits(((char*)pPgHdr->pData)+24, change_counter);
-
-      /* Also store the SQLite version number in bytes 96..99 and in
-      ** bytes 92..95 store the change counter for which the version number
-      ** is valid. */
-      put32bits(((char*)pPgHdr->pData)+92, change_counter);
-      put32bits(((char*)pPgHdr->pData)+96, SQLITE_VERSION_NUMBER);
+      /* Actually do the update of the change counter */
+      pager_write_changecounter(pPgHdr);
 
       /* If running in direct mode, write the contents of page 1 to the file. */
       if( DIRECT_MODE ){
@@ -43013,7 +43047,8 @@
   szPage = (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
   testcase( szPage<=32768 );
   testcase( szPage>=65536 );
-  if( pWal->hdr.mxFrame==0 ) return SQLITE_OK;
+  pInfo = walCkptInfo(pWal);
+  if( pInfo->nBackfill>=pWal->hdr.mxFrame ) return SQLITE_OK;
 
   /* Allocate the iterator */
   rc = walIteratorInit(pWal, &pIter);
@@ -43035,7 +43070,6 @@
   */
   mxSafeFrame = pWal->hdr.mxFrame;
   mxPage = pWal->hdr.nPage;
-  pInfo = walCkptInfo(pWal);
   for(i=1; i<WAL_NREADER; i++){
     u32 y = pInfo->aReadMark[i];
     if( mxSafeFrame>=y ){
@@ -43356,10 +43390,31 @@
 
   assert( pWal->readLock<0 );     /* Not currently locked */
 
-  /* Take steps to avoid spinning forever if there is a protocol error. */
+  /* Take steps to avoid spinning forever if there is a protocol error.
+  **
+  ** Circumstances that cause a RETRY should only last for the briefest
+  ** instances of time.  No I/O or other system calls are done while the
+  ** locks are held, so the locks should not be held for very long. But 
+  ** if we are unlucky, another process that is holding a lock might get
+  ** paged out or take a page-fault that is time-consuming to resolve, 
+  ** during the few nanoseconds that it is holding the lock.  In that case,
+  ** it might take longer than normal for the lock to free.
+  **
+  ** After 5 RETRYs, we begin calling sqlite3OsSleep().  The first few
+  ** calls to sqlite3OsSleep() have a delay of 1 microsecond.  Really this
+  ** is more of a scheduler yield than an actual delay.  But on the 10th
+  ** an subsequent retries, the delays start becoming longer and longer, 
+  ** so that on the 100th (and last) RETRY we delay for 21 milliseconds.
+  ** The total delay time before giving up is less than 1 second.
+  */
   if( cnt>5 ){
-    if( cnt>100 ) return SQLITE_PROTOCOL;
-    sqlite3OsSleep(pWal->pVfs, 1);
+    int nDelay = 1;                      /* Pause time in microseconds */
+    if( cnt>100 ){
+      VVA_ONLY( pWal->lockError = 1; )
+      return SQLITE_PROTOCOL;
+    }
+    if( cnt>=10 ) nDelay = (cnt-9)*238;  /* Max delay 21ms. Total delay 996ms */
+    sqlite3OsSleep(pWal->pVfs, nDelay);
   }
 
   if( !useWal ){
@@ -43441,22 +43496,9 @@
       mxI = i;
     }
   }
-  if( mxI==0 ){
-    /* If we get here, it means that all of the aReadMark[] entries between
-    ** 1 and WAL_NREADER-1 are zero.  Try to initialize aReadMark[1] to
-    ** be mxFrame, then retry.
-    */
-    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), 1);
-    if( rc==SQLITE_OK ){
-      pInfo->aReadMark[1] = pWal->hdr.mxFrame;
-      walUnlockExclusive(pWal, WAL_READ_LOCK(1), 1);
-      rc = WAL_RETRY;
-    }else if( rc==SQLITE_BUSY ){
-      rc = WAL_RETRY;
-    }
-    return rc;
-  }else{
-    if( mxReadMark < pWal->hdr.mxFrame ){
+  /* There was once an "if" here. The extra "{" is to preserve indentation. */
+  {
+    if( mxReadMark < pWal->hdr.mxFrame || mxI==0 ){
       for(i=1; i<WAL_NREADER; i++){
         rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1);
         if( rc==SQLITE_OK ){
@@ -43469,6 +43511,10 @@
         }
       }
     }
+    if( mxI==0 ){
+      assert( rc==SQLITE_BUSY );
+      return WAL_RETRY;
+    }
 
     rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
     if( rc ){
@@ -43529,6 +43575,10 @@
   do{
     rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
   }while( rc==WAL_RETRY );
+  testcase( (rc&0xff)==SQLITE_BUSY );
+  testcase( (rc&0xff)==SQLITE_IOERR );
+  testcase( rc==SQLITE_PROTOCOL );
+  testcase( rc==SQLITE_OK );
   return rc;
 }
 
@@ -43846,6 +43896,8 @@
     volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
     assert( pInfo->nBackfill==pWal->hdr.mxFrame );
     if( pInfo->nBackfill>0 ){
+      u32 salt1;
+      sqlite3_randomness(4, &salt1);
       rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
       if( rc==SQLITE_OK ){
         /* If all readers are using WAL_READ_LOCK(0) (in other words if no
@@ -43863,7 +43915,7 @@
         pWal->nCkpt++;
         pWal->hdr.mxFrame = 0;
         sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
-        sqlite3_randomness(4, &aSalt[1]);
+        aSalt[1] = salt1;
         walIndexWriteHdr(pWal);
         pInfo->nBackfill = 0;
         for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
@@ -43880,6 +43932,10 @@
       int notUsed;
       rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
     }while( rc==WAL_RETRY );
+    assert( (rc&0xff)!=SQLITE_BUSY ); /* BUSY not possible when useWal==1 */
+    testcase( (rc&0xff)==SQLITE_IOERR );
+    testcase( rc==SQLITE_PROTOCOL );
+    testcase( rc==SQLITE_OK );
   }
   return rc;
 }
@@ -47585,7 +47641,7 @@
                                    pageSize-usableSize);
       return rc;
     }
-    if( nPageHeader>nPageFile ){
+    if( (pBt->db->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
       rc = SQLITE_CORRUPT_BKPT;
       goto page1_init_failed;
     }
diff --git a/dist/sqlite3.h b/dist/sqlite3.h
index ac397da..140b77a 100644
--- a/dist/sqlite3.h
+++ b/dist/sqlite3.h
@@ -109,7 +109,7 @@
 */
 #define SQLITE_VERSION        "3.7.4"
 #define SQLITE_VERSION_NUMBER 3007004
-#define SQLITE_SOURCE_ID      "2010-12-07 20:14:09 a586a4deeb25330037a49df295b36aaf624d0f45"
+#define SQLITE_SOURCE_ID      "2011-02-20 03:40:59 e2616004dfaf61d776e448693971b6478552a635"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
diff --git a/dist/sqlite3.h.orig b/dist/sqlite3.h.orig
index 47ef256..ad3a3ee 100644
--- a/dist/sqlite3.h.orig
+++ b/dist/sqlite3.h.orig
@@ -109,7 +109,7 @@
 */
 #define SQLITE_VERSION        "3.7.4"
 #define SQLITE_VERSION_NUMBER 3007004
-#define SQLITE_SOURCE_ID      "2010-12-07 20:14:09 a586a4deeb25330037a49df295b36aaf624d0f45"
+#define SQLITE_SOURCE_ID      "2011-02-20 03:40:59 e2616004dfaf61d776e448693971b6478552a635"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers